- Multilayer Growth of Porphyrin-Based Polyurea Thin Film Using Solution-Based Molecular Layer Deposition Technique
- S. M. Nizam Uddin, Y. Nagao*
Langmuir, 33, 12777 - 12784 (2017)
We demonstrated a solution-based molecular layer deposition (MLD) approach to prepare porphyrin-based covalent organic molecular networks on a modified substrate surface using the urea coupling reaction at room temperature.
- Proton-Conductivity Enhancement in Polymer Thin Films (Invited Feature Article, Cover Art)
- Y. Nagao*
Langmuir, 33, 12547 - 12558 (2017)
This Feature Article presents a new approach to enhancing the proton conductivity of the polymer thin films using an interface that can modify the degrees of freedom for a polymer structure through interaction between the substrate surface and polymers.
- Development of Ion-Conductive and Vapoluminescent Porous Coordination Polymers Composed of Ruthenium(II) Metalloligand
- A. Watanabe, A. Kobayashi, E. Saitoh, Y. Nagao, S. Omagari, T. Nakanishi, Y. Hasegawa, W. M. C. Sameera, M. Yoshida, M. Kato
Inorg. Chem., 56, 3005 - 3013 (2017)
- In-plane oriented highly ordered lamellar structure formation of poly(N-dodecylacrylamide) induced by humid annealing
- Y. Hashimoto, T. Sato, R. Goto, Y. Nagao, M. Mitsuishi, S. Nagano, J. Matsui
RSC Advances, 7, 6631 - 6635 (2017)
- Fabrication of hydrazine sensor based on silica-coated Fe2O3 magnetic nanoparticles prepared by a rapid microwave irradiation method
- H. Akhter, J. Murshed, M. A. Rashed, Y. Oshima, Y. Nagao, M. M. Rahman, A. M. Asiri, M. A. Hasnat, M. N. Uddin, I. A. Siddiquey
J. Alloy. Compd., 698, 921 - 929 (2017)
A facile, efficient and rapid method for fabrication of silica-coated Fe2O3 magnetic nanoparticles (NPs) by a microwave (MW) irradiation method is reported.
- Effect of Casting Solvent on Interfacial Molecular Structure and Proton Transport Characteristics of Sulfonated Polyimide Thin Films (Selected as HOT article)
- Y. Nagao*, K. Krishnan, R. Goto, M. Hara, S. Nagano
Anal. Sci. (Special Issue), 33, 35 - 39 (2017)
Crystalline and amorpous parts are discussed in the sulfonated polyimide thin films to understand the proton transport property.
- Proton Conductivities of Lamellae-forming Bio-inspired Block Copolymer Thin Films Containing Silver Nanoparticles
- H. Yabu, J. Matsui, M. Hara, S. Nagano, Y. Matsuo, Y. Nagao
Langmuir, 32, 9484 - 9491 (2016)
Size-controlled metal nanoparticles (NPs) were spontaneously formed. The proton conductivity of well-aligned lamellae structured PVCa-b-PSt films with Ag NPs was evaluated. We found that the proton conductivity of PVCab-PSt film was increased 10-fold by the addition of Ag NPs into the proton conduction channels filled with catechol moieties.
The growth of metal–organic coordination network thin films on surfaces has been pursued extensively and intensively to manipulate the molecular arrangement.
The preparation of urea (bonded) cross-linked multilayer thin films by sequential deposition of bifunctional and tetrafunctional molecular building blocks is demonstrated. Molecular ordering and mass density increase in the surface normal direction of the substrate with a certain number of deposited layers.
- Inverse effects of supporting electrolytes on the electrocatalytic nitrate reduction activities in a Pt|Nafion|Pt-Cu type reactor assembly
- M. A. Hasnat, J. A. Safwan, M. A. Rashed, Z. Rahman, M. M. Rahman, Y. Nagao, A. M. Asiri
RSC Advances, 6, 11609 - 11617 (2016)
The effects of Cl− and SO42− ions on the electrocatalytic nitrate reduction activities in a sandwich-type reactor assembly are illustrated. It was noticed that a Pt|Nafion|Pt–Cu assembly offers its best efficiency in the absence of any supporting electrolytes.
- Hydrophobized Plant Polyphenol: Self-Assembly and Promising Antibacterial, Adhesive, and Anticorrosion Coatings
- D. Payra, M. Naito, Y. Fujii, Y. Nagao
Chem. Commun., 52, 312 - 315 (2016)
Hydrophobized plant polyphenol can be easily prepared by rational and controlled etherification of highly abundant aromatic hydroxyls with linear alkyl chains. The resultant organo-soluble polyphenols spontaneously formed fibrous structures and unravelled to be potential adhesive, anticorrosion, and antibacterial coatings.
Understanding the Nafion-Pt interface structure is important because fuel cell reactions occur at the three-phase boundary. However, the interface structure of the Nafion-Pt interface remains unclear. In this study, relationship between the proton transport property and thin film structure on the Pt-deposited surface at the three-phase boundary for fuel cells is discussed. Thickness dependence of the degree of orientation for this OP band was observed at the Nafion-Pt interface.
- Visualization of Ion-conductivity: Vapochromic Luminescence of an Ion-conductive Ru(II)-metalloligand-based Porous Coordination Polymer
- A. Watanabe, A. Kobayashi, E. Saitoh, Y. Nagao, M. Yoshida, M. Kato
Inorg. Chem., 54(23), 11058 - 11060 (2015)
An vapochromic luminescence enables visualization of the ion conductivity of the material by the color of the luminescence.
The effect of molecular ordering and ordered domain size on molecular weight dependent proton conductivity in well-organized sulfonated polyimide (SPI) thin films has been investigated.
- Modification for Uniform Surface of Nafion Ultra-thin Film Deposited by Inkjet Printing
- Y. Guo, Y. Ono, Y. Nagao*
Langmuir, 31 (37), 10137 - 10144 (2015)
We demonstrated the utilization of practical film-forming technique inkjet printing to fabricate a Nafion ultra-thin film less than 10nm thickness. Post-treatment in an ethanol vapor atmosphere exhibited a significant effect on flattening and homogenizing the film surface morphology. Results show that the well-distributed Nafion ultra-thin film modified by ethanol vapor annealing manifested much-improved proton conductivity.
- Anomalous Enhancement of Proton Conductivity for Water Molecular Clusters Stabilized in Interstitial Spaces of Porous Molecular Crystals
- M. Tadokoro, Y. Ohhata, Y. Shimazaki, S. Ishimaru, T. Yamada, Y. Nagao, T. Sugaya, K. Isoda, Y. Suzuki, H. Kitagawa, H. Matsui
Chemistry - A European Journal, 20(42), 13698 - 13709 (2014)
Proton conductivity of crystallized water clusters confined within low-dimensional nanoporous materials
- Influence of Confined Polymer Structure on Proton Transport Property in Sulfonated Polyimide Thin Films
- K. Krishnan, T. Yamada, H. Iwatsuki, M. Hara, S. Nagano, K. Otsubo, O. Sakata, A. Fujiwara, H. Kitagawa, Y. Nagao*
Electrochemistry, 82(10), 865 - 869 (2014)
The organized structure and proton transport property in sulfonated polyimide (SPI) thin ﬁlm have been studied. The high proton conductivity of 2.8 × 10−1 S cm−1 at 80°C and 90% RH was achieved in the highly oriented SPI thin ﬁlm. In contrast, the bulk SPI showed the drop of conductivity value at high relative humidity region, which is due to the signiﬁcant structural disorder accompanied by the strong interaction between the sulfonic acid side chains and water molecules.
- Surface proton transport of fully protonated poly(aspartic acid) thin films on quartz substrates
- Y. Nagao*, T. Kubo
Applied Surface Science, 323, 19 - 24 (2014)
Proton transport of fully protonated poly(aspartic acid) thin film was investigated. The thin film structure differed greatly from the partially protonated one. Proton transport occurs on the surface, not inside of the thin film. This result contributes to biological transport systems such as bacteriorhodopsin.
- Proton conductivity enhancement in oriented, sulfonated polyimide thin ﬁlms
- K. Krishnan, H. Iwatsuki, M. Hara, S. Nagano, Y. Nagao*
J. Mater. Chem. A, 2(19), 6895 - 6903 (2014)
Studies of proton transport in confined thin polymer electrolytes are essential for providing additional information regarding the structure–property relationships of such materials. Sulfonated polyimide film confined to a thickness of approximately 530 nm shows significant proton conductivity enhancement to a value of 2.6 × 10−1 S/cm (95% RH at 298 K).
- Effects of Nafion impregnation using inkjet printing for membrane electrode assemblies in polymer electrolyte membrane fuel cells
- Z. Wang, Y. Nagao*
Electrochim. Acta, 129, 343 - 347 (2014)
We present a method of using inkjet printing to deposit Nafion ionomer as the transport media onto catalyst layer made into membrane electrode assemblies (MEAs) for polymer electrolyte fuel cells (PEMFCs).
- Enhancement of Proton Transport in an Oriented Polypeptide Thin Film
- Y. Nagao*, J. Matsui, T. Abe, H. Hiramatsu, H. Yamamoto, T. Miyashita, N. Sata, H. Yugami
Langmuir, 29, 6798 - 6804 (2013)
Proton transport properties of a partially protonated poly(aspartic acid)/sodium polyaspartate (P-Asp) were investigated. A remarkable enhancement of proton conductivity has been achieved in the thin film. Proton conductivity of 60-nm-thick thin film prepared on MgO(100) substrate was 3.4 × 10–3 S cm–1 at 298 K.
- Substrate dependence of the proton transport and oriented structure in oligo[(1,2propanediamine)-alt-(oxalic acid)] thin films (Editor's choice)
- Y. Nagao*
Chem. Lett., 42, 468 - 470 (2013)
The molecular orientation in the thin film could be correlated with the proton-transport properties.
- Highly Oriented Sulfonic Acid Groups in a Nafion Thin Film on Si Substrate
- Y. Nagao*
J. Phys. Chem. C, 117, 3294 - 3297 (2013)
Nafion thin film on Si substrate had a highly oriented structure with the sulfonic acid groups at the side chain. The lower proton conductivity of the Nafion thin film was related with these highly oriented structures.
- Surface electronic structure of BaZr1-xYxO3-δ by soft-X-ray spectroscopy
- H. Tohru, F. Iguchi, Y. Nagao, N. Sata, Y. S. Liu, P. A. Glans, J. Guo, H. Yugami
Transactions of the Materials Research Society of Japan, 37, 575 - 578 (2012)
- A study on the plasma-treated surfaces of MgO(100) and quartz substrates by infrared multiple-angle incidence resolution spectrometry
- Y. Nagao*
e-Journal of Surface Science and Nanotechnology, 10, 229 - 233 (2012)
Contact angle measurements and an infrared p-polarized multiple-angle incidence resolution spectrometry (p-MAIRS) technique were performed on MgO(100) and quartz substrates.
- Proton transport property of Nafion thin films on MgO(100) with anisotropic molecular structure
- Y. Nagao*
e-Journal of Surface Science and Nanotechnology, 10, 114 - 116 (2012)
The proton conductivity of two thin films were quite lower values compared to that of the commercial Nafion membrane, and the thickness dependence of the proton conductivity was also observed.
- Photocurable Electrolyte Based on Sulfonated Poly(ether ether ketone)
- Y. Nagao*, T. Iwadera, N. Sata, F. Iguchi, H. Yugami
Solid State Ionics, 204-205, 35 - 40 (2011)
Protonconcutive photocurable electrolytes were prepared. Patterning of micro-structure on the photocured membrane was also demonstrated by using the property of the photocurable electrolytes.
- Catalytic activity of carbon-supported iridium oxide for oxygen reduction reaction as a Pt-free catalyst in polymer electrolyte fuel cell
- C. H. Chang, T. S. Yuen, Y. Nagao*, H. Yugami
Solid State Ionics, 197, 49 - 51 (2011)
Iridium oxide supported on Vulcan XC-72 carbon black (IrO2/C) as a cathode catalyst for polymer electrolyte fuel cell (PEFC) has been characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), cyclic voltammetry (CV). It was found that IrO2/C had high oxygen reduction reaction (ORR) activity. IrO2/C catalyst would be potential candidates for use as cathode catalyst in PEFC.
- Proton transport properties of poly(aspartic acid) with different average molecular weight
- Y. Nagao*, Y. Imai, J. Matsui, T. Ogawa, T. Miyashita
The Journal of Chemical Thermodynamics, 43, 613 - 616 (2011)
We synthesized seven partially protonated poly(aspartic acids)/sodium polyaspartates (P-Asp) with different average molecular weights to study their proton transport properties.
- Proton concentration in 15mol% Y-doped BaZrO3 proton conductors prepared at various temperatures
- F. Iguchi, Y. Nagao, N. Sata, H. Yugami
Solid State Ionics, 192, 97 - 100 (2011)
- Synthesis and Proton transport property of Poly(aspartic acid) thin film on SiO2 substrate
- Y. Nagao*, F. Iguchi, N. Sata, H. Yugami
Solid State Ionics, 181, 206 - 209 (2010)
Poly(aspartic acid) and its thin film were synthesized to study proton transport properties. The proton conductivity of the thin film is one order of magnitude higher than that of the pelletized Poly(aspartic acid). The activation energies for the proton conduction of the pelletized Poly(aspartic acid) and thin film are 0.65 and 0.53 eV, respectively.
- Electronic Structure of Sr-doped LaScO3 Single Crystal Annealed in Different Atmospheres
- Y. Nagao*, J. Liu, F. Iguchi, T. Higuchi, N. Sata, H. Yugami
Japanese Journal of Applied Physics, 49, 010208 (2010)
The electronic structure near the top of the valence band and the bottom of the conduction band for Sr-doped LaScO3 single crystal was investigated by X-ray absorption spectroscopy (XAS).
- Electrocatalytic activity of Iridium Oxide nanoparticles coated on carbon for oxygen reduction as cathode catalyst in PEFC
- C. H. Chang, T. S. Yuen, Y. Nagao*, H. Yugami
Journal of Power Sources, 195, 5938 - 5941 (2010)
The iridium oxide nanoparticles supported on Vulcan XC-72 porous carbon were prepared for cathode catalyst in polymer electrolyte fuel cell (PEFC). The catalyst has been characterized by transmission electron microscopy (TEM) and in PEFC tests. The iridium oxide nanoparticles, which were uniformly dispersed on carbon surface, were 2–3 nm in diameter. With respect to the oxygen reduction reaction (ORR) activity was also studied by cyclic voltammetry (CV), revealing an onset potential of about 0.6 V vs. an Ag/AgCl electrode. The ORR catalytic activity of this catalyst was also tested in a hydrogen–oxygen single PEFC and a power density of 20 mW cm−2 has been achieved at the current density of 68.5 mA cm−2. This study concludes that carbon-supported iridium oxide nanoparticles have potential to be used as cathode catalyst in PEFC.
- Proton conductivity of oligomeric poly[(1, 2-propane-diamine)-alt-(oxalic acid)] thin films on Al2O3
- Y. Nagao*, N. Naito, F. Iguchi, N. Sata, H. Yugami
e-Journal of Surface Science and Nanotechnology, 7, 530 - 532 (2009)
Proton transport properties of three thin films (110, 240, and 360 nm thick films) on R-plane (1102) sapphire substrates for oligomeric poly[(1, 2-propanediamine)-alt-(oxalic acid)] were investigated. The maximum proton conductivity of the thin film is 1.7 × 10-3 S cm-1 at the RH of 80%, which is five times higher than that of the bulk sample (3.0 × 10-4 S cm-1). The activation energies of the 110, 240, and 360 nm thick films are found to 0.74, 0.67, and 0.68 eV at the RH of 80%, respectively.
- Synthesis of oligomeric poly[(1, 2-propanediamine)-alt-(oxalic acid)] and anomalous proton conductivities of the thin films
- Y. Nagao*, N. Naito, F. Iguchi, N. Sata, H. Yugami
Solid State Ionics, 180, 589 - 591 (2009)
New proton-conductive polyamide oligomers, oligomeric poly[(1, 2-propanediamine)-alt-(oxalic acid)], were synthesized to investigate the proton transport properties of bulk and thin films. The proton conductivity of thin film is relatively higher than that of bulk sample. Thickness dependence of the proton conductivity was observed in these thin films.
- Synthesis and Proton Transport Property of Poly(aspartic acid) Thin Film on MgO(100) Substrate
- Y. Nagao*, M. Ando, H. Maekawa, C. H. Chang, F. Iguchi, N. Sata，
ECS Transactions, 16, 401 - 406 (2009)
- The relationship between chemical composition distributions and specific grain boundary conductivity in Y-doped BaZrO3 proton conductors
- F. Iguchi, T. Tsurui, N. Sata, Y. Nagao, H. Yugami
Solid State Ionics, 180, 563 - 568 (2009)
- Electronic Structure of La1-xSrxScO3 Probed by Soft-X-Ray Absorption Spectroscopy
- T. Higuchi, Y. Nagao, J. Liu, F. Iguchi, N. Sata, T. Hattori, H. Yugami
Journal of Applied Physics, 104, 076110 (2008)
- Synthesis and protonic conductivity of the oligomeric amides with different average molecular weights
- Y. Nagao*, A. Haneda, N. Naito, F. Iguchi, N. Sata, H. Yugami
Solid State Ionics, 179, 1142 - 1145 (2008)
- Proton conductivity of biopolymer-platinum nanoparticle composite under high humidity
- M. Fujishima, H. Takatori, K. Yamai, Y. Nagao, H. Kitagawa, K. Uchida
Journal of Materials Science, 43, 9, 3130 - 3134 (2008)
- Performance of BaZrO3 based Proton Conductors as an Electrolyte for Intermediate Temperature Operating SOFC
- F. Iguchi, T. Tokikawa, T. Miyoshi, T. Tsurui, Y. Nagao, N. Sata, H. Yugami
ECS Transactions, 7, 2331 - 2336 (2007)
- Structures and phase transition of multi-layered water nanotube confined to nanochannels
- M. Tadokoro, S. Fukui, T. Kitajima, Y. Nagao, S. Ishimaru, H. Kitagawa, K. Isobe, K. Nakasuji
Chemical Communications, 12, 1274 - 1276 (2006)
- Preparation and proton transport property of N, N'-diethyldithiooxamidatocopper coordination polymer
- Y. Nagao, T. Kubo, K. Nakasuji, R. Ikeda, T. Kojima, H. Kitagawa
Synthetic Metals, 154, 89 - 92 (2005)
A novel proton-conductive copper coordination polymer, (H5C2)2dtoaCu (R2dtoaH2 = dithiooxamide derivatives), was synthesized. The proton conductivity (σp) was 4.2 × 10−6 S cm−1 under the RH of 100% and the ionic transport number was more than 0.99. The σp of (HOH4C2)2dtoaCu was two orders of magnitude higher than that of (H5C2)2dtoaCu, which would be derived from the existence of-OH groups in the alkyl substituent R.
- A new proton-conductive copper coordination polymer, (HOC3H6)2dtoaCu (dtoa = dithiooxamide)
- Y. Nagao, R. Ikeda, K. Iijima, T. Kubo, K. Nakasuji, H. Kitagawa
Synthetic Metals, 135-136, 283 - 284 (2003)
A new copper coordination polymer, (HOC3H6)(2)dtoaCu (dtoa = dithiooxamide), was synthesized. The a.c. conductivity measurements with an impedance analyzer were carried out for (HOC3H6)(2)dtoaCu in order to estimate the proton conductivity (sigmap).
- Substituent effect on the magnetic properties of copper coordination polymers with dithiooxamide and N, N'-bis-(hydroxyethyl)dithiooxamide
- M. Fujishima, Y. Nagao, R. Ikeda, S. Kanda, H. Kitagawa
Synthetic Metals, 133-134, 433 - 435 (2003)
- Highly proton-conductive copper coordination polymers
- Y. Nagao, M. Fujishima, R. Ikeda, S. Kanda, H. Kitagawa
Synthetic Metals, 133-134, 431 - 432 (2003)
AC conductivity measurements were carried out for a two-dimensional coordination polymer, N,N′-bis-(2-hydroxyethyl)dithiooxamidatocopper(II) with an impedance analyzer in order to estimate the protonic conductivity. This polymer was found to exhibit a high protonic conduction of σp=1.2×10−5 S cm−1 under relative humidity of 83% and 300 K.
- Highly proton-conductive copper coordination polymer, H2dtoaCu (H2dtoa = dithiooxamide anion)
- H. Kitagawa, Y. Nagao, M. Fujishima, R. Ikeda, S. Kanda
Inorganic Chemistry Communications, 6, 346 - 348 (2003)
Room-temperature proton conductivity, coordination geometry, and pore-diameter distribution of the title Cu(II) coordination polymer have been investigated by AC conductivity, EXAFS, and N2 adsorption isotherm measurements. The AC proton conductivity (σp) obtained from Cole–Cole plot analysis under relative humidity of 75% and 300 K exhibits a considerable high value of as a room-temperature σp. The mechanism of proton conduction seems to be similar to that of a proton-exchange membrane, Nafion, which contains much cluster of water molecules in the porous space of the polymer. The present Cu coordination polymer was revealed to possess porous space of about 6 Å, which includes much water molecules more than 10H2O per unit cell. The dimeric Cu(II) square-planar coordination geometry was confirmed by EXAFS analysis using synchrotron radiation source at SPring-8.
- Complex-Plane Impedance Study on A Hydrogen-Doped Copper Coordination Polymer,N,N'-bis-(2-hydroxyethyl)dithiooxamidatocopper(II)
- Y. Nagao, R. Ikeda, S. Kanda, Y. Kubozono, H. Kitagawa
Molecular Crystals and Liquid Crystals, 79, 89 - 94 (2002)
AC conductivity measurements with an impedance analyzer were carried out for a hydrogen-doped coordination polymer, N , N '-bis-(2-hydroxyethyl)dithiooxamidatocopper(II), in order to estimate the protonic condctivity. The log proton conductiivty was linearly increased from 2.6x10-9 to 2.2 x 10-6 S cmwith relative humidity (RH) from 45 to 100% at 300 K. A slight hysteresis of protonic conductivity was observed upon increasing and decreasing RH, which implies that H3O+ is generated by a reaction between water molecule and acid-base polymer near RH∼100%.